缩尺沙丘演化特性的风洞实验研究

Experiment on Evolution of Downsized Dunes in Wind Tunnel

以风洞实验为手段,从俯视和侧视2个角度采用光学测量同步记录、分析了缩尺沙丘的演化特性。结果表明:在风蚀沙床提供沙补给的情况下,缩尺沙丘的形态逐渐向新月形沙丘演化;沙丘的侵蚀主要发生在背风面,侵蚀程度随沙丘宽高比的减小而增大,迎风面仅在演化的初始阶段略有侵蚀,随后廓线基本保持不变;在同一时刻背风面和迎风面的侵蚀率均随沙丘宽高比的减小而增加,且随时间的推移逐渐降低,侵蚀率在背风面趋于定值,在迎风面逐渐逼近0。对沙丘宽高比进行关联性分析表明,沙丘的侵蚀程度和宽高比呈现单调变化关系,宽高比可作为参数独立描述沙丘的演化特性。

An experiment in a wind tunnel was conducted to record the evolution of downsized dunes from both top and side view by using an optical test system. The results show that downsized dunes gradually developed into barchans with sand supply given by the wind erosion on a sand bed. A further analysis on the profile variation indicates that the dunes erosion occurred mainly on the leeward side, and the erosion increased with the decrease in the ratio of the dune width and height. However, on the windward side, the erosion only occurred at the initial stage of the evolution and subsequently remained nearly unchanged. The erosion rate approached a nonzero constant on the leeward side while zero on the windward side as time went on. In addition, the relevance analysis on the dune width and height shows a clear monotonic relationship between dune erosion and the ratio of the dune width and height, so the ratio can be used as an independent parameter to describe the evolution of dunes.